Current disposal technology for palm oil mill sludge (POMS) creates problems such as sludge flooding insects, and bad odor mainly during the rain season. This study we present in-vessel composting system as an alternative process for disposal of POMS. Maximum temperature achieved for reactor was about 40

C. It can be verified that the composting process followed -1k first order kinetic equation with degradation rate =

0. 014 day with maximum degradation

rate of 51%. POMS compost has potential to improve performance of

C. citratus growth in sandy soil that usually lacks nutrients and has poor soil structure.

cleaning up processes in the mill that contains used to stabilize many types of industrial sludges and, hence, will contain cellulosic material, fat, oil, from pulp and paper mill, sugar, oleochemical, and grease (Agamuthu, 1995). Currently, most pig rearing, and olive milling. Composting is palm oil mill wastewater treatment methods are attractive because it can reduce the volume/ comprised of anaerobic pond/digester followed weight of sludge. Besides that, the composted by either aerobic pond or aerobic and facultative sludge is easy to handle and can be used as soil pond. Biological treatment and presence of conditioner, thus providing additional income suspended solids from influent generated palm (Rahman, Kahlil, and Yaser 2003). oil mill sludge (POMS) that accumulate at the

A.Y. Zahrim, A.A. Rakmi, and M.S. Kalil

The physicochemical analysis of the mixture bottom of the digester/pond must be desludged is shown in Table 1. The bioreactor was made after undergoing biological treatment to maintain from cylindrical polyethylene vessel measuring the efficiency of wastewater treatment. In 0.9m (height) by 0.6m (diameter). For aeration

Malaysia, POMS is usually dried up and then purposes, holes with 2cm diameter each were used as fertilizer. Drying is done in open ponds, made at the bottom of the bioreactor (Figure 1). but during the rainy season, the process creates problems such as sludge flooding, insects, and bad odor.

On another note, the burning of sawdust from sawmills and furniture industries can also create air pollution problems. Mixing POMS with sawdust can improve the efficiency of the composting process by increasing porosity, retaining nutrient, reducing odor, and providing 0.6 m additional carbon (Bhamidimarri and Pandey

1996). Using sawdust as amendment in compost 2 cm mixture can also reduce air pollution.

METHODOLOGYMaterials and BioreactorFigure 1. Bottom View of In-vessel System

Sludge from an anaerobic digestion pond was collected from Sri Ulu Langat Palm Oil Mill in Dengkil, Selangor, Malaysia. Sawdust Pot Trial was collected from various furniture factories around Bangi, Selangor. Then 52kg sludge Pseudostems of

C. citratus were bought from

and 28kg sawdust were manually mixed. market and submerged in tap water. After 3 days, 3 Mixture of POMS–sawdust was put in 0.3m

C. citratus plants that had leaves approximately

bioreactor. Experiments were done in duplicate. 0.5 cm long and roots approximately 0.5cm long

were transferred to 2-liter plastic pots. The pots Organic matter loss was determined using a were filled with different volumes of sand (bought formula given by [Paredes et al. 2000]: from a hardware shop) and compost or sludge.

The plants were placed on the cement floor put OM loss (%) = 100 – 100 x (A/B) (2) under the sun, and watered with distilled water every 2 days. No additional nutrient was added where, to the distilled water. After 2 months, the plants, excluding roots, were harvested, dried, and a = %Initial ash content x (100 – %Final ash weighted by putting the leaves and pseudostems content), and in a beaker. All experiments were done in six replicates. b = %Final ash content x (100 – %Initial ash content) .

Sampling and Analysis

Sampling was done by taking 40g of

RESULTS AND DISCUSSION

compost at four different heights (0, 0.3, 0.6, and 0.9m from bottom of the bin). The mixture

Temperature Evolution

was manually homogenized. Wet density was estimated by filling a 500mL beaker with material (Schulze, 1962). The pH was determined by

40

adding 5g sample to 50mL distilled water,

Ambient

mixed with magnetic stirrer for 20min, let stand for 24h, and then filtered (Barrington et al.

Compost

2003). The supernatant was tested using pH

35 mass

meter (HI 931401, Microprocessor, pH meter,

C

Hanna Instrument Ltd) . For moisture content, the mixture was ovendried at 103 C for 24h. Ovendried samples were finely ground and

Curve fitting of the experimental data which due to mesophilic organisms recommencing gave the following parameter values: it is justified activity. Distinct troughs in the temperature may 2 by r , also be due to the excessive presence of ammonia and phenols, which inhibit bacterial growth and

A = 51.0%

activity. Once most of the ammonia and phenols 2 r = 0.9926 are released to the air, the bacterial population

From Figure 4, the plant that grew on profile during composting, as determined by the untreated sludge media had the lowest yield (i.e. OM loss, followed a first order kinetic equation

-1 combination of pseudostems, leaves, and roots) with a degradation rate of 0.014 day and a compared with treated sludge and sand alone.

maximum OM loss of 51%. Palm oil mill–sawdust Jimenez and Garcia (1989) stated that unstabilized compost mixed with sand improved the growth waste causes a reduction in the metabolic rate of of

C. citratus. Thus, composting can be a suitable

plants and a decrease in root respiration, nutrient method for converting palm oil mill sludge into synthesis, and absorption capability. Other than compost that can be used as a pot/container that, the transportation of cytokinin and gibrelin growing medium. slows down.

C. citratus in media with treated sludge REFERENCES

(compost) has the highest yield, possibly due Agamuthu, P. (1995). Palm oil mill effluent— to the stabilized nutrient content of the compost

M.A. Hashim and P. Agamuthu, Editors, content in POMS compost is comparable with

Waste treatment plant. Narosa Publishing

other industrial sludge compost. Nogueira House, New Delhi. 338–360. Nogueira, and Devens (1999) stated that good Aggelides, S.M., and P.A. Londra. (2000). compost should have a P and K content of more

“ Effects of compost produced from town than 0.5% and 1.5% respectively. Thus, POMS waste on the physical properties of a loamy compost shows the potential to improve the and clay soil.” Bioresource Technology 71, performance of

C. citratus growth in sandy soil 253-253.

that usually lacks nutrients and has a poor soil APHA. (1985). Standard Methods for structure. th

Examination Water and Wastewater, 16 edn. American Public Health Association,

CONCLUSION Washington, DC.

During the composting process in an in- Bhamidimarri, S.M.R., and Pandey, S.P. (1996). vessel system, the maximum temperature for the Aerobic thermophilic composting of piggey